The unpopularity of the principle of organic unities shows very clearly how great is the danger of the assumption of unproved additive formulas. The fallacy, of which ignorance of organic unity is a particular instance, may perhaps be mathematically represented thus: suppose f(x) is the goodness of x and f(y) is the goodness of y. It is then assumed that the goodness of x and y together is f(x) + f(y) when it is clearly f(x + y) and only in special cases will it be true that f(x + y) = f(x) + f(y). It is plain that it is never legitimate to assume this property in the case of any given function without proof.

Since econometrics doesn’t content itself with only making optimal predictions, but also aspires to explain things in terms of causes and effects, econometricians need loads of assumptions — most important of these are additivity and linearity. Important, simply because if they are not true, your model is invalid and descriptively incorrect. It’s like calling your house a bicycle. No matter how you try, it won’t move you an inch. When the model is wrong — well, then it’s wrong.

One answer is that economists don’t listen to themselves. More precisely, liberal economists like Krugman who want the state to take a more active role in managing the economy, continue to teach an economic theory that has no place for activist policy.

Let me give a concrete example.

One of Krugman’s bugaboos is the persistence of claims that expansionary monetary policy must lead to higher inflation. Even after 5-plus years of ultra-loose policy with no rising inflation in sight, we keep hearing that since so “much money has been created…, there should already be considerable inflation” … As an empirical matter, of course, Krugman is right. But where could someone have gotten this idea that an increase in the money supply must always lead to higher inflation? Perhaps from an undergraduate economics class? Very possibly — if that class used Krugman’s textbook.

Here’s what Krugman’s International Economics says about money and inflation:

“A permanent increase in the money supply causes a proportional increase in the price level’s long-run value. … we should expect the data to show a clear-cut positive association between money supplies and price levels. If real-world data did not provide strong evidence that money supplies and price levels move together in the long run, the usefulness of the theory of money demand we have developed would be in severe doubt …

A permanent increase in the level of a country’s money supply ultimately results in a proportional rise in its price level but has no effect on the long-run values of the interest rate or real output.”

This last sentence is simply the claim that money is neutral in the long run, which Krugman continues to affirm on his blog …

You might think these claims about money and inflation are unfortunate oversights, or asides from the main argument. They are not. The assumption that prices must eventually change in proportion to the central bank-determined money supply is central to the book’s four chapters on macroeconomic policy in an open economy …

So these are not throwaway lines. The more thoroughly a student understands the discussion in Krugman’s textbook, the stronger should be their belief that sustained expansionary monetary policy must be inflationary. Because if it is not, Krugman gives you no tools whatsoever to think about policy …

Liberal Keynesian economists made a deal with the devil decades ago, when they conceded the theoretical high ground. Paul Krugman the textbook author says authoritatively that money is neutral in the long run and that a permanent increase in the money supply can only lead to inflation. Why shouldn’t people listen to him, and ignore Paul Krugman the blogger?

Keynes’s insights have enormous practical importance, according to Lance Taylor and Duncan Foley [who jointly received the Leontief Prize for Advancing the Frontiers of Economic Thought at Tufts University’s Global Development and Environment Institute on Monday.]

But isn’t Keynes now mainstream? No, say Foley and Taylor. The mainstream still sees economies as inherently moving to an optimal equilibrium … It still says demand causes short-run fluctuations, but only supply factors, such as the capital stock and technology, can affect long-run growth.

EVEN PAUL KRUGMAN, a self-described Keynesian, Nobel laureate, and New York Times columnist, writes in the 2012 edition of his textbook: “In the long run the economy is self-correcting: shocks to aggregate demand affect aggregate output in the short run but not in the long run” …

Krugman does point to one exception: If interest rates are nearly zero, as during the financial crisis, markets lose restorative force. But, Taylor asks, what’s the logic?

Keynes saw capitalism’s general state as allowing almost arbitrary unemployment: hence his “General Theory.” Full employment was a lucky exception.

To Taylor, calling full employment the general state and allowing one unlucky exception turns Keynes upside down. And look where this confusion has brought us, he adds. Take the current eurozone disaster. For two decades, the European Union bureaucracy in Brussels, the German Council of Economic Experts, and a chorus of others, branded Germany, the “sick man of Europe,” as suffering from a sclerotic supply side: rigid labor unions, impediments to layoffs, a burdensome welfare state. But German labor costs to produce output sank steadily, and Germany generated huge trade surpluses — hardly signs of a sclerotic supply side. Yet growth has barely averaged 1 percent a year since 2000.

I can’t but agree with Taylor and Foley here. To a large degree one does get the impression that Krugman thinks he is a Keynesian because he is a stout believer in John Hicks IS-LM interpretation of Keynes.

In a post on his blog, self-proclaimed “proud neoclassicist” Paul Krugman has argued that “Keynesian” macroeconomics more than anything else “made economics the model-oriented field it has become.” In Krugman’s eyes, Keynes was a “pretty klutzy modeler,” and it was only thanks to Samuelson’s famous 45-degree diagram and Hicks’s IS-LM that things got into place. Although admitting that economists have a tendency to use ”excessive math” and “equate hard math with quality” he still vehemently defends — and always have — the mathematization of economics:

I’ve seen quite a lot of what economics without math and models looks like — and it’s not good.

However, being a student of Hyman Minsky, yours truly very much doubt that IS-LM is an adequate reflection of the width and depth of Keynes’s insights on the workings of modern market economies.

Almost nothing in the post-General Theory writings of Keynes suggests him considering Hicks’s IS-LM anywhere near a faithful rendering of his thought. In Keynes’s canonical statement of the essence of his theory — in the famous 1937 Quarterly Journal of Economics article — there is nothing to even suggest that Keynes would have thought the existence of a Keynes-Hicks-IS-LM-theory anything but pure nonsense. John Hicks, the man who invented IS-LM in his 1937 Econometrica review of Keynes’ General Theory — “Mr. Keynes and the ‘Classics’. A Suggested Interpretation” — returned to it in an article in 1980 — “IS-LM: an explanation” — in Journal of Post Keynesian Economics. Self-critically he wrote that ”the only way in which IS-LM analysis usefully survives — as anything more than a classroom gadget, to be superseded, later on, by something better — is in application to a particular kind of causal analysis, where the use of equilibrium methods, even a drastic use of equilibrium methods, is not inappropriate.”

IS-LM is typically set in a current values numéraire framework that definitely downgrades the importance of expectations and uncertainty — and a fortiori gives too large a role for interests as ruling the roost when it comes to investments and liquidity preferences. Reducing uncertainty to risk — implicit in most analyses building on IS-LM models — is nothing but hand waving. According to Keynes we live in a world permeated by unmeasurable uncertainty — not quantifiable stochastic risk — which often forces us to make decisions based on anything but “rational expectations.” Keynes rather thinks that we base our expectations on the “confidence” or “weight” we put on different events and alternatives. To Keynes expectations are a question of weighing probabilities by “degrees of belief,” beliefs that often have preciously little to do with the kind of stochastic probabilistic calculations made by the rational agents as modeled by “modern” social sciences. And often we “simply do not know.”

IS-LM not only ignores genuine uncertainty, but also the essentially complex and cyclical character of economies and investment activities, speculation, endogenous money, labour market conditions, and the importance of income distribution. Most of the insights on dynamic coordination problems that made Keynes write General Theory are lost in the translation into the IS-LM framework.

Sure, “New Keynesian” economists like Krugman — and their forerunners, “Keynesian” economists like Paul Samuelson and (young) John Hicks — certainly have contributed to making economics more mathematical and “model-oriented.”

But if these math-is-the-message-modelers aren’t able to show that the mechanisms or causes that they isolate and handle in their mathematically formalized macromodels are stable in the sense that they do not change when we “export” them to our “target systems,” these mathematical models do only hold under ceteris paribus conditions and are consequently of limited value to our understandings, explanations or predictions of real economic systems.

The kinds of laws and relations that “modern” economics has established, are laws and relations about mathematically formalized entities in models that presuppose causal mechanisms being atomistic and additive. When causal mechanisms operate in real world social target systems they only do it in ever-changing and unstable combinations where the whole is more than a mechanical sum of parts. If economic regularities obtain they do it (as a rule) only because we engineered them for that purpose. Outside man-made mathematical-statistical “nomological machines” they are rare, or even non-existant. Unfortunately that also makes most of contemporary mainstream neoclassical endeavours of mathematical economic modeling rather useless. And that also goes for Krugman.

In recent blogposts Paul Krugman has come back to his idea that it would be great if the Fed stimulated inflationary expectations so that investments would increase. I don’t have any problem with this idea per se, but I don’t think it’s of the stature that Krugman seems to think. But although I have written extensively on Knut Wicksell and consider him the greatest Swedish economist ever, I definitely – since Krugman portrays himself as “sorta-kinda Keynesian” – have to question his invocation of Knut Wicksell for his ideas on the “natural” rate of interest. Krugman writes (emphasis added):

Start with the very simplest view of how Fed policy affects the economy: the Fed sets short-term interest rates, and other things equal a lower rate leads to higher output; the “natural rate” of interest … is the rate at which output equals potential, that is, at which there are neither inflationary nor deflationary pressures …

What does this tell us? First of all, that there is nothing “artificial” or “unnatural” about low interest rates; they’re low because demand is low, and the Fed is responding appropriately. If anything, the “unnatural” situation is that rates are too high, because they’re constrained by the zero lower bound (rates can’t go below zero, except for some minor technical bobbles, because people can always just hold cash).

Second, the Fed’s inability to get rates as low as they should be justifies a search for policies that can fill this policy gap. Fiscal stimulus is one such policy; unconventional monetary policies of various kinds are another. Actually, the natural policy — natural in a Wicksellian sense, and also the one that in terms of standard economics should produce the least distortion — would be a credible commitment to higher inflation.

In my Treatise on Money I defined what purported to be a unique rate of interest, which I called the natural rate of interest¾namely, the rate of interest which, in the terminology of my Treatise, preserved equality between the rate of saving (as there defined) and the rate of investment. I believed this to be a development and clarification of Wicksell’s ‘natural rate of interest’, which was, according to him, the rate which would preserve the stability of some, not quite clearly specified, price-level.

I had, however, overlooked the fact that in any given society there is, on this definition, a different natural rate of interest for each hypothetical level of employment. And, similarly, for every rate of interest there is a level of employment for which that rate is the ‘natural’ rate, in the sense that the system will be in equilibrium with that rate of interest and that level of employment. Thus it was a mistake to speak of the natural rate of interest or to suggest that the above definition would yield a unique value for the rate of interest irrespective of the level of employment. I had not then understood that, in certain conditions, the system could be in equilibrium with less than full employment.

I am now no longer of the opinion that the [Wicksellian] concept of a ‘natural’ rate of interest, which previously seemed to me a most promising idea, has anything very useful or significant to contribute to our analysis. It is merely the rate of interest which will preserve the status quo; and, in general, we have no predominant interest in the status quo as such.

Paul Krugman has on his blog tried to explain why we should still use the neoclassical hobby horse Aggregate Supply-Aggregate Demand model:

So why do AS-AD? … We do want, somewhere along the way, to get across the notion of the self-correcting economy, the notion that in the long run, we may all be dead, but that we also have a tendency to return to full employment via price flexibility. Or to put it differently, you do want somehow to make clear the notion (which even fairly Keynesian guys like me share) that money is neutral in the long run.

Actually, this is the same unsubstantiated stuff you find in all of the “fairly Keynesian” Greg Mankiw’s textbooks.

Well, THIS “fairly Keynesian” guy is not impressed. And I doubt that Keynes himself would have been impressed by having his theory being characterized with catchwords like “tendency to return to full employment” and “money is neutral in the long run.”

As Taylor and Foley convincingly argue — Krugman is no real Keynesian.

Added GMT 1630: In case you still think that Keynes shared Krugman’s concern of getting across “the notion of the self-correcting economy, the notion that in the long run, we may all be dead, but that we also have a tendency to return to full employment via price flexibility” — well, have a look at this 1934 BBC radio address by Keynes, and you will certainly come to think differently [h/t Sandwichman].

Statistical Science is not really very helpful for understanding or forecasting complex evolving self-healing organic ambiguous social systems – economies, in other words.

A statistician may have done the programming, but when you press a button on a computer keyboard and ask the computer to find some good patterns, better get clear a sad fact: computers do not think. They do exactly what the programmer told them to do and nothing more. They look for the patterns that we tell them to look for, those and nothing more. When we turn to the computer for advice, we are only talking to ourselves …

Mathematical analysis works great to decide which horse wins, if we are completely confident which horses are in the race, but it breaks down when we are not sure. In experimental settings, the set of alternative models can often be well agreed on, but with nonexperimental economics data, the set of models is subject to enormous disagreements. You disagree with your model made yesterday, and I disagree with your model today. Mathematics does not help much resolve our internal intellectual disagreements.

Based on the [quantity theory of money equation MV = PQ] holding the money velocity constant, if the money supply (M) increases at a faster rate than real economic output (Q), the price level (P) must increase to make up the difference. According to this view, inflation in the U.S. should have been about 31 percent per year between 2008 and 2013, when the money supply grew at an average pace of 33 percent per year and output grew at an average pace just below 2 percent. Why, then, has inflation remained persistently low (below 2 percent) during this period? …

During the first and second quarters of 2014, the velocity of the monetary base2 was at 4.4, its slowest pace on record. This means that every dollar in the monetary base was spent only 4.4 times in the economy during the past year, down from 17.2 just prior to the recession. This implies that the unprecedented monetary base increase driven by the Fed’s large money injections through its large-scale asset purchase programs has failed to cause at least a one-for-one proportional increase in nominal GDP. Thus, it is precisely the sharp decline in velocity that has offset the sharp increase in money supply, leading to the almost no change in nominal GDP (either P or Q).

So why did the monetary base increase not cause a proportionate increase in either the general price level or GDP? The answer lies in the private sector’s dramatic increase in their willingness to hoard money instead of spend it. Such an unprecedented increase in money demand has slowed down the velocity of Money …

And why then would people suddenly decide to hoard money instead of spend it? A possible answer lies in the combination of two issues:
•A glooming economy after the financial crisis
•The dramatic decrease in interest rates that has forced investors to readjust their portfolios toward liquid money and away from interest-bearing assets such as government bonds.

Until a few years ago, economists of all persuasions confidently proclaimed that the Great Depression would never recur. In a way, they were right. After the financial crisis of 2008 erupted, we got the Great Recession instead. Governments managed to limit the damage by pumping huge amounts of money into the global economy and slashing interest rates to near zero. But, having cut off the downward slide of 2008-2009, they ran out of intellectual and political ammunition.

Economic advisers assured their bosses that recovery would be rapid. And there was some revival; but then it stalled in 2010. Meanwhile, governments were running large deficits – a legacy of the economic downturn – which renewed growth was supposed to shrink. In the eurozone, countries like Greece faced sovereign-debt crises as bank bailouts turned private debt into public debt.

Attention switched to the problem of fiscal deficits and the relationship between deficits and economic growth. Should governments deliberately expand their deficits to offset the fall in household and investment demand? Or should they try to cut public spending in order to free up money for private spending?

Depending on which macroeconomic theory one held, both could be presented as pro-growth policies. The first might cause the economy to expand, because the government was increasing public spending; the second, because they were cutting it. Keynesian theory suggests the first; governments unanimously put their faith in the second.

The consequences of this choice are clear. It is now pretty much agreed that fiscal tightening has cost developed economies 5-10 percentage points of GDP growth since 2010. All of that output and income has been permanently lost. Moreover, because fiscal austerity stifled economic growth, it made the task of reducing budget deficits and national debt as a share of GDP much more difficult. Cutting public spending, it turned out, was not the same as cutting the deficit, because it cut the economy at the same time.

This modeling convention … makes it virtually impossible to incorporate concerns that are central to heterodox economics: liquidity preference, power in finance, predatory behavior, illiquid asset markets, increasing inequality in income and wealth …

One possibly decisive structural change has yet to be — and perhaps cannot be — acknowledged through DSGE modeling: the fact that most nations in the global North are simultaneously pursuing austerity policies. It is obvious in trade theory that every nation in a global trading system cannot maintain a surplus on current account. But this obvious result, which is an implication of a regime in which nation after nation is pursuing austerity macroeconomic policies, cannot be expressed in a macroeconomics based on models that focus almost completely on intertemporal coordination, while ignoring point-in-time structural interconnections.

The obsession with government budget deficits since the crisis of 2008 and the subsequent recession illustrates the damage done by mistaken economic ideas. In the rich West, tens of millions of people lost jobs that could have been saved …

The media focused on the politics of the budget debate, but economic ideas had a central role in the outcome. Believers in Say’s law predominated … The most prominent research was led by Alberto Alesina of Harvard University, where conservative economists had displaced much of the formerly pro-government liberal faculty of the 1960s … Cut deficits, went Alesina’s argument, and you will restore the business confidence to invest fully the excess savings; spending cuts were more effective than tax increases in reducing deficits.

Alesina’s research was poor. Most important, his analysis, which started in the early 1990s, didn’t distinguish the economic conditions under which austerity policies were adopted. Essentially, Alesina’s optimistic conclusions about austerity expansions applied only when economies were already strengthening or their currencies were falling in value sufficiently to spur export — conditions not applicable to either the United States or most of Europe.

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